An effective cleaning reagent and cleaning procedures are necessary for automated and semi-automated blood analyzers for cleaning the instrument components that are in contact with the blood samples, or the mixtures of a blood sample and the reagents used for blood analysis, and maintaining the analyzers in proper operating conditions. During blood sample analysis, for example on automated hematology analyzers, the whole blood sample will be treated with various reagents on the instrument prior to the measurement. Typically, an aliquot of a whole blood sample is diluted by an isotonic diluent to form a sample mixture for the red blood cell and platelet measurements. Another aliquot of the whole blood sample is mixed with a lytic reagent to form a second sample mixture for the white blood cell and hemoglobin measurements, wherein the red blood cells are lysed. These sample mixtures of the blood sample and the reagents contain proteins, and debris from the lysed cellular membranes. These materials can precipitate on the surface of certain instrument components which are in contact with the sample mixtures during the analysis of the blood sample. Furthermore, these materials can also form insoluble complexes with certain chemicals in the reagent and precipitate on the surface of the instrument components. Without an effective cleaning on a regular basis, the precipitates can build up around the apertures and flow cell, which are used for blood cell counting, and along the wall of tubings that are in contact with the sample mixtures. This can cause partial or complete clogging of the apertures or flow cell, rendering the instrument inoperable.
Enzymatic cleaning reagents are known in the art, and they are effective in breaking down the proteins and blood debris by enzymatic reactions. Surfactants are commonly used in the cleaning reagents for dissolving or dispersing the debris and large organic molecules.
Antimicrobials are commonly used in the cleaning reagents as preservatives to inhibit the growth of microorganisms, such as bacteria, fungi, and yeast, and to ensure shelf-life, quality and performance of the reagent products. Furthermore, it is also important to prevent microorganism growth inside the instruments, such as inside the reagent tubings and other parts of the fluid feeding system, because organism growth can cause contamination of the instrument components, and can further interfere with system performance. For example, the organisms can be counted as blood cells, or cause false flaggings which indicate the presence of abnormal blood types in a blood sample.
The majority of commonly used antimicrobials are formaldehyde-releasing agents, which contain or release formaldehyde during storage. These formaldehyde-releasing agents are strong antimicrobials and are very effective in inhibiting the growth of organisms in aqueous solutions. However, the formaldehyde contained in a cleaning reagent released through the instrument effluent has caused environmental concerns in recent years.
In the past decade, the regulations for institutional, industrial and medical waste content increase as certain chemicals are found to pose a threat to human health and/or to the environment. Regulation agencies in several states, such as California and Massachusetts, have implemented new regulations on waste content allowance. Formaldehyde is one of the chemicals that are restricted in the waste in these two states. According to the new regulation, formaldehyde concentration in the waste equal or less than 1 ppm is considered formaldehyde-free.
Therefore, there is a strong need for a formaldehyde-free cleaning reagent that is effective cleaning the blood analyzers, stable during storage, and environmentally friendly.